Dear Frankie tells the story of a mother who hires a stranger to pose as her son's long lost father. The real father was an abuser from whom she has run away and hid her child. She does so to perpetuate the myth she has created for her son through letters she has forged over the years.

Actress Emily Mortimer, who plays the mother, felt the film addressed parents' eternal dilemma in a dramatic way. "I think that that's a choice that actually mothers and fathers make a lot," she said. "We, usually to a much lesser degree, find ourselves in the position of keeping the brutal truth from our children for as long as is humanly possible. And we do it in lots of different ways. It's as simple as not wanting to let them know that Father Christmas isn't real, you know. Things like that, and it's interesting because I think it raises a really good question as to how long that sort of state of innocence should carry on, and whether or not in some ways we're just protecting ourselves more than anything else. It's for the sentimental notion or nostalgic notion of our own innocence, and loss of it, that we want to save our children from the truth, which actually they can probably handle much better than we give them credit for."

Therefore, Mortimer ultimately disagrees with her character's actions in the film. "I think probably she shouldn't have, but then people behave, thank God, not perfectly, and that's the point of [movies]. You watch other people sort of screwing up and feel better about your own screw ups. And I do know of a lot of people in my life who have lied to their children about big things, for a long time. And as I say, I think it is an error often, because very often, children are much more sophisticated and able to cope with the gray areas of life, than we give them credit for. Or than we are, you know. They can cope with honesty better than we can."

Gerard Butler plays the stranger, and he addressed the social issue of lying to kids with a bit of humor. "I love it when you ask me to comment on society and life and politics," Butler said. "I'm an actor. But I'm going to do it anyway. I can't you're believe you're making me do it. This sick, sick woman who was already misleading this child who was deaf and mute, and the last thing he needs is his mother making up stories. No. I completely understood that lie because she did it and I kind of felt that that was the difference between me and The Stranger because I thought it was more interesting to play The Stranger as a person who when he hears the story he thinks, 'This is the most insane story I've ever heard. How did this happen?' But with me, I completely understand. Maybe I'm just more sensitive to mothers having been brought up by a single mother who had three children and she did it on her own. But I think that this is one of the beautiful things about this movie. What people do to help others that they love, and it might not be the perfect thing, but it's the best thing that they know how to do at that time. There's a lot of that going on in this movie. There are different characters all with their own kind of wounded souls in a way, trying to help each other, and they don't always go about it in the best way, and everyone has a different view on how to help. But at the end of the day it leaves you feeling, despite the fact that I've never known anyone who can feel so melancholy, but at the same time feel so uplifting and that's what it does. It's uplifting because in some ways there's a kind of triumph of the human spirit. Everyone is trying their best."

The Stranger bonds with Frankie over the course of two days in what begins as a business transaction for the Stranger, according to Butler. "I always thought that The Stranger was a bit of a loner to be honest, but when you come back into town you have friends that you would see. He very much keeps himself to himself though. He's not necessarily comfortable around people and he's especially not very comfortable with little kids. His father probably wasn't very comfortable with him. He didn't have that close connection with his own parents, especially his dad. I couldn't help thinking that in all of those first moments he was thinking, 'What am I doing here? I really wish that I wasn't going through this.' And what I found interesting was that when he brought the present to the boy, I don't think that he did that out of goodness. It's just that if he was going to do a job he was going to do it well because at the end of the day what you realize is that here's a man of integrity and when he knew that he had that job to do, he said, 'Well, I've got to read these letters.' And when he read the letters he thought, 'Well, I better make this convincing and what's going to make it convincing is if I buy this little boy a book about sea life because then he'll buy it more.' I couldn't help thinking about like, I mean imagine you standing there and the little kid walks in and he looks at you, it's like trying to get into a club with someone else's ID, and someone goes, 'That's not you.' And to me, that's the most humiliating experience on the planet, when you're caught in a bare face lie to someone. I think that freaks me out more than it freaks out most people. I've just always had a problem with that. I'm not saying that I don't lie. I do. But it's just that when you know it's a public situation that you can be found out in, where someone could say, 'You're lying.' If the boy said, 'That's not my dad,' what would I do? Would I say, 'No. I am.' Or 'No. You're right. I'm just kidding. Goodbye.' So I felt that one of the main things in his mind was, 'I just better get this right. I have to make sure that this is as convincing as possible.' And then suddenly I'm there and I really don't kind of want to be there, and I have to connect. But as an audience, when you watch little Frankie and what is wonderful about little Frankie is that he's not someone that you'd necessarily feel sorry for. He's not written in that way. He's a spunky little kid. He doesn't feel sorry for himself. He enjoys his life. He's smart. He's no one's fool. That's what I get as well. I suddenly see this little kid and I start thinking about what a life he's had, and actually where the mother is coming from and what she'll have to become involved in. He thinks, 'You know what, give a bit of yourself here.' I think that I identify as well with what happens to him, The Stranger. It's a beautiful plot point. It's a beautiful piece of writing. It's a lovely relationship and it was just there."

Since the audience learns nothing about The Stranger's past in the film, Butler had no backstory of his own to go on. "I kind of just used myself. I have so many connections with the story. If there's one thing that I can do as an actor is I can connect strongly with my characters. It's one of the reasons that I chose them. In some ways, I have some similar history to what Frankie had. I spent many years without my dad not knowing where he was or whether he was alive and there are many facets of my character that are like The Stranger. So you focus more on them. But at the same time, I think that it's more complicated than saying, 'I'm just blank.' Or that I would create a whole back story. This isn't for everyone, but I think that for me what was so fascinating about The Stranger was that the less you knew about the guy the better. The fact that you just had no idea of who he was, where he came from left you thinking, 'What is he going to do? How is going to act?' So I guess it was a bit of both which is kind of a strange answer, but that's what worked for me."

Mortimer had a bit more work to do as Frankie's mother. Particularly, since he was deaf, she had to convincingly speak sign language. "I learned what I had to, for the part. But I would love to investigate it more, I think it's an amazing language, an amazing way of communicating. And there was something just so there and present, and it's incredibly sort of visceral, talking to someone who's deaf. And you really feel, you've got just their full attention, and it's all incredibly intense and wonderful. And I think that signing is a very direct way of communicating, and I'm very taken by that whole deaf world. But I didn't, I'm ashamed to say, I didn't have enough time to really, I mean it's a big thing, it's like learning a whole language. So I didn't get to the bottom of it."